701.二叉搜索树中的插入操作.cpp

/*
 * @lc app=leetcode.cn id=701 lang=cpp
 *
 * [701] 二叉搜索树中的插入操作
 */
struct TreeNode {
  int val;
  TreeNode *left;
  TreeNode *right;
  TreeNode() : val(0), left(nullptr), right(nullptr) {}
  TreeNode(int x) : val(x), left(nullptr), right(nullptr) {}
  TreeNode(int x, TreeNode *left, TreeNode *right)
      : val(x), left(left), right(right) {}
};
// @lc code=start
/**
 * Definition for a binary tree node.
 * struct TreeNode {
 *     int val;
 *     TreeNode *left;
 *     TreeNode *right;
 *     TreeNode() : val(0), left(nullptr), right(nullptr) {}
 *     TreeNode(int x) : val(x), left(nullptr), right(nullptr) {}
 *     TreeNode(int x, TreeNode *left, TreeNode *right) : val(x), left(left),
 * right(right) {}
 * };
 */
class Solution {
public:
  TreeNode *insertIntoBST(TreeNode *root, int val) {
    if (root == nullptr)
      return new TreeNode(val);
    else if (root->val > val) {
      root->left = insertIntoBST(root->left, val);
    } else if (root->val < val) {
      root->right = insertIntoBST(root->right, val);
    }
    // todo 写在里面和写在外面有啥区别
    return root;
  }
};
// @lc code=end